In application control networks, such as—but not limited to—lighting control networks, data forwarding devices, are used to forward messages between different application control components, such as sensors and actuator of a lighting application. It is known from Heller et all, “ElasticTree: Reducing Energy in Data Center Networks”, that present data-forwarding devices like data-forwarding devices are inefficient at low load. Presently, when being in an idle status—that is powered but not used for communication—a typical data-forwarding device uses only 5% less power compared to when these status in which the data-forwarding device is fully loaded with data transmission.
In wired application control environments an application device may be powered via Power Over Ethernet (i.e. PoE). From DE 10 2008 035544 A1 it is known to switch off respective PoE end devices by switching off the power supply to these end devices via a controllable switch integrated in the network card the respective end devices are connected to. An intermediate PoE device, such as a data-forwarding device, however, is an all ports on/off device, just like a normal Ethernet data-forwarding device without Power Over Ethernet functionality. A typical PoE data-forwarding device will thus require a relative high additional power budget to “keep the line alive”. This is standardized in Ethernet standard “802.3 at” (i.e. “Eight-oh-two-dot-three-Alfa-Tango”). The Ethernet standard 802.3at for Power Over Ethernet requires a minimum standby power of 250 mW per port. In big installations with many nodes this amounts to large standby-power, not only from data communication equipment such as e.g. data-forwarding devices such as but not limited to data-switches and routers but also from the nodes that are attached thereto, such as electrical actuators/loads or sensors. This causes several problems:                Large standby power generates heat and degrades the life of electronics, unless it is overdesigned to cope with that, which results in extra cost.        Application end notes with large energy saving potentials such as LED's in the lighting sector, may become less substantial due to the standby power consumed by the data communication network.        More ambitious requirements on “Energy Performance Calculations” for new buildings and/or renovations and reductions in energy use are expected in the context of sustainability.        Energy loss in itself results in non negligible costs in moderate to large buildings.        Energy loss of devices usually heats the surrounding air, which requires additional cooling, which in itself consumes additional energy and thus produces costs.        
PoE equipment cannot be sent to ‘sleep’, meaning that the equipment is switched off entirely, since a PoE device would have to maintain a network interface in order to be able to receive a wake up command and therefore a PoE device requires power which it receives via Ethernet as well. But also switching off components with external power supply within the network might influence to overall network performance in an un-desired way, for instance, data paths may be cut off or be unduly prolonged.